1. Field of the Invention
This invention relates to a recording sheet on which an ink jet printer prints a monochromatic or full-color image at a high speed by jetting droplets of water-color ink or the like and, more particularly, to an ink jet recording sheet suitable for observing an image from the reverse side of a base.
2. Description of the Related Art
As recording methods, thermal fusion transfer methods, thermal sublimation transfer methods, electrophotographic methods using a toner as a medium, ink jet methods and the like are known. Recently, the application of ink jet recording methods has been increased because this kind of recording method is advantageous in terms of noiselessness during recording, high-speed printing performance, color recording facility, and adaptability to recording of a large image.
The following are qualities required in an ink jet recording sheet:
(1) an improved ink absorptivity and a blurring-free property,
(2) improved smoothness and glossiness,
(3) sheet/image waterproofness such that ink does not run or spread when water is attached to the sheet,
(4) stability in size such that the sheet does not slacken when it absorbs a large amount of water, and
(5) a high developed color density and improved sharpness of an image.
Various improvement techniques have been developed to obtain such qualities. With respect to a sheet having an image seen from the rear side, i.e., a back print sheet, the inventions disclosed in Japanese Patent Laid-Open Publication Nos. 62-222876, 62-242576 and 63-34176 are known.
However, if an ink jet printer is used to print an image on the above-described conventional recording sheets, most of dyestuff components in ink pass through an ink receiving layer to reach a base. The developed color density of the resulting image is not high enough to suitably appreciate the image when the image is seen from the ink receiving layer, although the image can be seen as a good image when seen from the reverse side of the base.
This problem will be described in more detail. The ink receiving layer in the conventional recording sheets is formed of an ink permeable layer and an ink fixation layer. The ink permeable layer is provided only for passage of ink dyestuffs and an ink solvent. The ink fixation layer is provided on the basis of a concept of achieving an ink absorbing effect only by using a water absorptive resin. Therefore, the ink absorption layer does not absorb organic solvent components such as diethylene glycol, triethylene glycol monomethyl ether and triethylene glycol monoethyl ether, although it absorbs water in the ink solvent. Accordingly, the organic solvent components stay on the interface between the ink permeable layer and the ink fixation layer. On the other hand, the ink dyestuffs have a property such as to cohere basically to the organic solvent and are, therefore, fixed at the interface between the ink permeable layer and the ink fixation layer. However, the fixation of the dyestuffs is considerably unstable since the ink permeable layer has no dyestuff fixing function.